Rule #1 before reading further. Nothing I am going to say should be construed as an attack on your personally.
What we have here is "availability vs. choice". It may be available when they are 8 or 10, but if they are choosing to watch it (and at that age, someone is letting them) is another thing. That "choice" is what the parents can influence. You need to control, as much as you can, availability until you get a chance to talk to them about right/wrong and the choices they make. You can get PPV on your cable box now... hopefully you have a pin, or lock, on those channels to prevent younger children from watching inappropriate matter.
Yea, I know... sometimes kids do whatever they want no matter what you tell them. Contrary to what society tells us, I believe this to be the exception not the rule. I firmly believe that kids today are more a reflection of their parents, and how they were raised, then a reflection of society. Sure, society seems to try and screw us up at every turn, but we are the one's who have the responsibility to mold our offspring.
Full Disclosure: Both my kids are grown, with kids of their own. I'm not trying to mold two young girls in today's society where something such as a "slut walk" is considered acceptable or "empowering". I feel for today's parents because I know society doesn't help, but on the other hand I'm not a big believer in the "it takes a village" theory that everyone needs to be involved either.

